利用核磁共振技术监测海带湿面贮藏品质

利用低场核磁共振技术监测2种贮藏条件下海带湿面样品弛豫特性的变化,探讨水分及其迁移变化规律,测定产品质构性质的变化,分析二者的相关性。真空包装的海带湿面样品分别于常温、4℃和-18℃条件下贮藏。以弛豫时间T2、质子密度M2、质构特性为主要指标。监测贮藏期间其品质变化规律。试验结果表明:常温、4℃和-18℃3种贮藏条件下水分迁移及质构特性变化的关键时期依次为28~35,35~42,49~56 d。弛豫特性与质构特性呈显著相关。     

Internal Hollows in Cooked Rice Grains (Oryza sativa cv. Koshihikari) Observed by NMR Micro Imaging

Nondestructive analysis of water distribution and structural changes in cooked rice grains, Oryza sativa cv Koshihikari, was performed with Nuclear Magnetic Resonance (NMR) Micro imaging of protons (¹H). Using a specially designed holder, high quality images of cooked rice grains were obtained, even when up to 10 grains were studied simultaneously. Internal hollows were observed in all examined cooked rice grains, and we propose a mechanism to explain their formation. The origin of these hollows was hypothesized to be cracks or fissures, and hollows resulted from sealing of such lacerations by gelatinized starch in the peripheral layer in combination with expansion of the grain during cooking.     

大米浸泡过程水分状态变化的低场核磁共振研究

对3种大米浸泡过程中的水分状态进行低场核磁共振(LF-NMR)测定。通过对糯米浸泡过程中水分状态变化的研究得出:水分进入到糯米中心所需的浸泡时间最短为35min,浸泡加水量最少为35%;水温在15～30℃范围内,每升高5℃,糯米达到相同水分状态的浸泡时间可以缩短10min;不同品种大米浸泡过程中水分状态变化呈现明显的差异,浸泡1h后,表征自由水分的T23大小依次为:糯米(37.64ms)、粳米(52.63ms)和籼米(59.94ms)。     

利用核磁共振技术研究鱼糜制品在储藏过程中的水分变化

利用核磁共振技术(NMR)监测鱼糜制品相应的自旋-自旋弛豫时间T2以及各组分水的含量变化。研究墨鱼丸、花枝丸两种鱼糜制品在-18℃(正常储藏温度)以及4℃/-18℃(扩大化模拟冷库温度变化)两种储藏条件下各种水分的分布和迁移情况。结果表明:这两种鱼糜制品具有4种流动性不同的水分,其对应的弛豫时间分别为T21、T22、T23、T24(0ms相似文献   

冷藏山羊肉品质变化的核磁共振研究

利用低场核磁共振技术,研究了冷藏山羊肉中结合水、不易流动水和自由水的分布和变化情况。结果表明,羊肉中的结合水弛豫时间(T21)和不易流动水弛豫时间(T22)以及二者与总水分相对含量随冷藏时间的变化呈现明显的下降趋势,并且T21、T22与羊肉的滴水损失、pH、肉色有显著的相关性;低场核磁共振技术(LF-NMR)能够很好地表征山羊肉冷藏期间有关水分及品质变化情况,可用于山羊肉冷藏的货架期快速检测。     

Observation of the Structure, Moisture Distribution, and Oil Distribution in the Coating of Tempura by NMR Micro Imaging

ABSTRACT: The 3-layered fine structure of the coating of the Japanese oil-fried battered food, tempura, was observed by nuclear magnetic resonance micro imaging. The porosity of the intermediate layer was correlated to the moisture content of the batter. Chemical shift imaging, which gave moisture distribution and oil distribution images, revealed the changes in the coating after cooking. The oil was detected to a depth of only 1 mm in the outer layer immediately after frying, and its distribution slightly expanded in the surface layer with time after frying. Water quickly transferred from bean curd (tofu) as 1 ingredient, to the coating along the porous network wall within 25 min after frying.     

利用低场核磁共振技术分析冬瓜真空干燥过程中的内部水分变化

为研究冬瓜真空干燥过程中内部水分的含量、分布及状态变化,应用低场核磁共振（low-field nuclearmagnetic resonance,LF-NMR）技术,测定不同干燥条件下冬瓜真空干燥过程中的横向弛豫时间T2反演谱,进而分析冬瓜样品内部的水分状态及其变化规律。结果表明：在真空干燥过程中,冬瓜干基含水率与NMR信号幅值之间呈显著的线性关系;真空干燥过程改变了样品的横向弛豫时间T2,增加了冬瓜内部不易流动水的含量、降低了水分的流动性;不同干燥温度条件下,结合水所占比例、自由水所占比例随着干燥时间的变化分别呈指数模型、多项式模型,且拟合方程的决定系数均大于0.95,拟合精度较高。该研究为进一步研究产品的保藏提供技术指导,为冬瓜的真空干燥实际产业化生产控制提供理论依据。     

Formulation of Caking-Resistant Powdered Soups Based on NMR Analysis

ABSTRACT: This study demonstrates that the caking tendencies of powdered soups could be altered by adjusting the proportions of existing ingredients in the recipes without using anticaking chemicals. The composition adjustment was guided by the knowledge of the caking tendencies of individual ingredients, which was acquired with a low field nuclear magnetic resonance (NMR) instrument. This study showed that increasing the proportions of caking-resistant ingredients in soup recipes lowered the caking tendency. Multiple regression models based on the data from NMR experiments and storage tests were used for prediction of days-until-caking (DUC) values of soup products stored at different temperatures (37 to 65°C).     

利用LF-NMR技术分析油桃干燥过程中内部水分的变化

为研究油桃内部水分分布及干燥过程中水分迁移规律,为油桃的保藏及加工提供新思路。利用LF-NMR技术测定了不同含水量油桃的信号强度与水分含量的关系及水分分布情况,并测定了不同干燥方式的油桃片横向弛豫时间(T2)的变化,进而分析了油桃内部水分状态及变化规律。研究结果表明:油桃的含水量与信号强度呈显著正相关,拟合方程为:y=12.415x-596.67(R2=0.9822);MRI图像可以清晰反映油桃的果肉、核壳、核仁儿等结构及其水分分布情况;新鲜油桃中含有三种状态的水,分别是结合水、不易流动水和自由水,其中自由水约为90%,结合水约为1%,剩下的为不易流动水;干燥处理能够降低水分的自由度,T2值减小,且鼓风干燥的T2减小速度比真空干燥的快;鼓风干燥过程中不易流动水向自由水迁移,自由水向外迁移散失,而真空干燥中的自由水一部分向外迁移散失,另一部分向不易流动水迁移。该研究为油桃的保藏与干燥实际产业化生产控制提供理论依据。     

利用低场核磁共振技术研究调味山药片真空微波干燥过程中水分的变化规律

为研究调味山药片真空微波干燥过程中内部水分含量、分布及状态变化情况,采用低场核磁共振技术,测定不同微波功率下微波真空干燥过程中的横向弛豫时间T2反演谱,进而分析调味山药片内部的水分状态及其变化规律。结果表明：微波功率越高,自由水和不易流动水被除去所需的时间越短,其中对自由水作用尤为明显,但过高的微波功率会导致物料出现焦化现象;调味山药片干基含水率与核磁共振总峰面积之间呈线性关系,可以预测调味山药片真空微波干燥达到干燥终点所需的时间。核磁共振图像显示调味山药片干燥过程中水分含量的增加和减少均是由外而内,干燥结束时,剩余水主要存在于调味山药内层。水分含量的变化对调味山药片干燥后的品质有显著影响,低场核磁共振及成像技术为调味山药片干燥过程中水分的变化提供了直观的参考依据,本研究可以为调味山药片的真空微波脆化工艺设计、优化干燥参数、控制干燥过程及提高产品质量提供参考。     

The significance of cooling rate on water dynamics in porcine muscle from heterozygote carriers and non-carriers of the halothane gene-a low-field NMR relaxation study

The post mortem changes in the chemical/physical state distribution of water were followed in pig muscle (M. longissimus dorsi) from heterozygote (n=12) and non-carriers (n=12) of the halothane gene exposed to two different cooling profiles using continuous low-field NMR relaxation measurements. T₂ relaxation data were analyzed using distributed exponential fitting analysis. Independent of genotype post mortem changes were observed in the two water populations characterizing water within the myofibrillar space (T₂₁) and the extra-myofibrillar space (T₂₂), respectively, as a function of chilling regime. The effect was most pronounced in samples from heterozygote carriers of the halothane gene. The obtained results strongly suggest that improved water-holding capacity of muscles upon fast chilling can be ascribed to a reduced accumulation of extra-myofibrillar water in the meat post mortem, and it is hypothesized that differences in the accumulation of extra-myofibrillar water post mortem can be ascribed largely to the time at which disruption of cell membrane integrity takes place.     

NMR和MRI技术对面包和奶酪二元体系在贮藏过程中水分迁移的研究(英文)

采用低场核磁共振成像技术中的spin3D、CPMG等序列对面包和奶酪二元体系进行成像并测定自旋-自旋弛豫时间等参数,并对其在贮藏过程中水分迁移行为及规律进行了研究,为核磁共振技术在食品中的应用打下良好的基础。     

Magnetic Resonance Imaging of Meat Products: Automated Quantitation of the NMR Relaxation Parameters of Cured Pork,by Both ‘bulk’ NMR and MRI Methods

An integrated protocol has been developed for the automated acquisition and processing of a set of magnetic resonance images which quantify the spatial distribution of the T₁ and T₂ values, proton density (M₀) and magnetisation transfer (MT)-rate. That protocol has been validated for homogeneous samples against ‘ bulk’ NMR measurements using the same experimental conditions, both at 2·35 and 7 Tesla. Application of that technology to pork cured in a brine solution shows that brining affected the T₂ values and the apparent MT rates more significantly than either the T₁ values, the M₀ values or the M_sat/M₀ ratios. The dependence of the NMR relaxation times on meat swelling induced by sodium chloride is also discussed.     

低场核磁共振在肉与肉制品水分测定与分析中的应用研究进展

低场核磁共振是一种近年来快速发展的检测分析技术,该技术在肉与肉制品的水分测定及相关研究中的应用越来越广泛,所取得的成果亟需总结。因此,本文阐述了低场核磁共振技术在肉与肉制品水分测定中的工作原理,分析了低场核磁共振技术在肉与肉制品生产、加工和贮藏过程中水分分布与迁移规律,肉制品的食用品质和加工品质的检测,以及肉制品掺假判定和新鲜度检测等方面的应用,以期为促进低场核磁共振技术在肉与肉制品加工和品质控制中的应用提供理论依据。     

Magnetic resonance imaging (MRI) and relaxation spectrum analysis as methods to investigate swelling in whey protein gels

Effective means for controlled delivery of nutrients and nutraceuticals are needed. Whey protein-based gels, as a model system and as a potential delivery system, exhibit pH-dependent swelling when placed in aqueous solutions. Understanding the physics that govern gel swelling is thus important when designing gel-based delivery platforms. The extent of swelling over time was monitored gravimetrically. In addition to gravimetric measurements, magnetic resonance imaging (MRI) a real-time noninvasive imaging technique that quantified changes in geometry and water content of these gels was utilized. Heat-set whey protein gels were prepared at pH 7 and swelling was monitored in aqueous solutions with pH values of 2.5, 7, and 10. Changes in dimension over time, as characterized by the number of voxels in an image, were correlated to gravimetric measurements. Excellent correlations between mass uptake and volume change (R(2)= 0.99) were obtained for the gels in aqueous solutions at pH 7 and 10, but not for gels in the aqueous solution at pH 2.5. To provide insight into the mechanisms for water uptake, nuclear magnetic resonance (NMR) relaxation times were measured in independent experiments. The relaxation spectrum for the spin-spin relaxation time (T(2)) showed the presence of 3 proton pools for pH 7 and 10 trials and 4 proton pools for pH 2.5 trials. Results demonstrate that MRI and NMR relaxation measurements provided information about swelling in whey protein gels that can constitute a new means for investigating and developing effective delivery systems for foods.     

Relationships between sensory perception and water distribution determined by low-field NMR T(2) relaxation in processed pork - impact of tumbling and RN(-) allele

The relationships between water distribution, measured with low-field NMR (LF-NMR) transverse (T₂) relaxometry and sensory properties in tumbled and non-tumbled cured-smoked loins from 30 female Hampshire crossbred pigs were investigated. Upon distributed analysis of the T₂ relaxation, three populations centred at about 2, 40 and 600–800 ms, respectively, were detected. Clear differences in the characteristics of the intermediate population (T₂₁) were observed between loins from carriers and non-carriers of the RN⁻ allele, which implies differences in water–protein interactions between the two genotypes. PLS regressions between NMR T₂ variables and sensory attributes revealed significant correlations between NMR T₂ variables and the sensory attributes juiciness, acidulous taste and meat taste, which mainly could be ascribed to the T₂₁ time constant. In addition, the number of unappealing pores assessed by the sensory panel was highly related to the relative T₂ populations, implying that the microstructure is directly reflected in the NMR T₂ populations. However, prediction of the processing yield from NMR T₂ variables was poor. The correlation improved when RN genotypes and tumbling conditions were included as predictors. Thus, other effects of tumbling treatments and RN genotypes unrelated to NMR T₂ relaxation were observed.     

Water properties and salt uptake in Atlantic salmon fillets as affected by ante-mortem stress,rigor mortis,and brine salting: A low-field H NMR and H/Na MRI study

A low-field (LF) ¹H NMR T₂ relaxation and ²³Na/¹H MRI study was performed on Atlantic salmon to study the effect of ante-mortem handling stress and rigor mortis on muscle water properties and subsequent post-rigor salting. Compared to rested fish, exhausted fish exhibited a more rapid and stronger development of rigor mortis. This resulted in significant differences in post-rigor water-holding capacity and salt uptake. By LF NMR T₂ relaxation analysis significant differences in water distribution according to (1) ante-mortem handling, (2) fillet location, and (3) brine salting were detected. Furthermore, ²³Na MRI revealed differences between the two treatments in fillet salt distribution, where the salt penetration in exhausted fillets was more pronounced. By combining ¹H and ²³Na MR images, the salt diffusion and distribution seemed to be highly affected by the distribution of fat.     

柑橘皮黄酮石灰水提取工艺及果胶去除效果的研究

以柑橘皮为原料,通过单因素及正交试验优化石灰水法提取柑橘皮黄酮的工艺条件,同时对石灰水提取法、NaOH提取法和乙醇提取法的黄酮得率以及黄酮提取液中的果胶含量进行比较。单因素及正交试验结果表明:以稀释4倍的饱和石灰水为提取剂,液料比为30 mL/g、90℃水浴2 h,黄酮得率最高为(5.15±0.03)mg/g。不同提取法的比较结果表明:石灰水法的黄酮得率与NaOH法相当,高于乙醇法;石灰水法的黄酮提取液中果胶略高于乙醇法,但远低于NaOH法。石灰水法不仅能有效地提取柑橘皮黄酮,也可以降低对杂质果胶的提取率。     

A review of botanical characteristics, phytochemistry, clinical relevance in efficacy and safety of Lycium barbarum fruit (Goji)

Lycium barbarum has been used as a traditional Chinese medicine (TCM) to nourish liver and kidney, and brighten the eye. The fruits are dried or freshly squeezed for their juice and concentrated for beverages. Among various constituents, a group of polysaccharides (LBP) with a Glycan-O-Ser glycopeptide structure has been most researched and considered to be important for the efficacy of L. barbarum. Studies indicate effects of L. barbarum on aging, neuroprotection, general well-being, fatigue/endurance, metabolism/energy expenditure, glucose control in diabetics, glaucoma, anti-oxidant properties, immunomodulation, anti-tumor activity and cytoprotection. In addition to TCM, L. barbarum can be sold as a dietary supplement or classified as a food based upon the long and safe traditional usage. This review is to provide background and updated information of chemical constituents and efficacies with safety including a new direction for research and current regulatory situation of L. barbarum.